The MHRA was keen to stress the “extremely rare rate of occurrence” of these events of CSVT.
Sinus vein thrombosis is a condition where a blood clot forms in the cerebral vein in the brain.
Symptoms of this condition include headache, blurred vision, fainting or loss of consciousness.
The medicines regulator emphasised people should still get their vaccine when offered due to the rarity of these symptoms.
So far there have been five cases of CSVT which equates to a rate of one in one million people vaccinated.
These five cases were men aged 19 to 59 who experienced a clot along with low blood platelet count.
One of the five has since died according to the MHRA.
The European Medicines Agency has said the Oxford/AstraZeneca jab is a “safe and effective vaccine”, the regulator’s executive director Emer Cooke said.